Method and Apparatus for Heating or Cooling

ABSTRACT

Embodiments of the subject invention pertain to a method and apparatus for heating or cooling. Embodiments relate to a method and apparatus utilizing a vapor compression cycle to accomplish active heating or cooling. In a specific embodiment, the subject invention relates to a lightweight, compact, reliable, and efficient heating or cooling system for underwater applications. The subject system can provide heating or cooling stress relief to individuals operating under, for example, hazardous conditions, or in low temperature underwater environments where passive protective clothing provides insufficient mitigation of cooling stress. Further embodiments can be utilized to provide heat stress relief to users who are working in thermally encapsulated ensembles that hinder the body&#39;s natural ability to expel heat. The subject system can be utilized in other applications that can benefit from this type of heating or cooling system. The performance of this system cannot be matched simply by using smaller versions of currently available designs or technologies.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application Ser. No. 61/056,357, filed May 27, 2008, which is hereby incorporated by reference herein in its entirety, including any figures, tables, or drawings.

FIELD OF INVENTION

The subject invention relates to microclimate heating or cooling, and a miniature heating or cooling system, that can be used for any purpose that requires a compact heating or cooling system. Such applications include, but are not limited to, personal and portable heating or cooling systems.

BACKGROUND OF THE INVENTION

Deep submersion operations performed by free-swimming divers, such as Navy divers, often expose them to extremely cold conditions. Currently, there is no effective and/or efficient method of heating divers during exposure to such conditions. This deficiency can induce cold stress, which in turn impairs diver performance, shortens dive duration, and creates an unnecessary health risk to divers. The issue usually arises during cold water dives, and the affects of the cold typically manifest first in the diver's extremities, such as hands and feet.

Currently available solutions, such as electrical resistor type systems, which at maximum can only supply as much heat as the electrical power expended for unit operation, are inefficient and require large amounts of portable power supplies. Other alternative solutions, such as umbilical chord attachments to the diver that can supply warm water and electrical power, are also too bulky and significantly restrict the user's freedom of movement.

Accordingly, there is need for a heating system having a high coefficient of performance and a light compact design. The solution should heat effectively to maintain core body temperatures. The solution should preferably be low profile, small volume, power efficient, resistant to corrosive saltwater, and operate for the duration of a typical dive.

BRIEF SUMMARY

Embodiments of the subject invention pertain to a method and apparatus for heating or cooling. Embodiments relate to a method and apparatus utilizing a vapor compression cycle to accomplish active heating or cooling. In a specific embodiment, the subject invention relates to a lightweight, compact, reliable, and efficient heating or cooling system for underwater applications. The subject system can provide heating or cooling stress relief to individuals operating under, for example, hazardous conditions, or in low temperature underwater environments where passive protective clothing provides insufficient mitigation of cooling stress. Further embodiments can be utilized to provide heat stress relief to users who are working in thermally encapsulated ensembles that hinder the body's natural ability to expel heat. The subject system can be utilized in other applications that can benefit from this type of heating or cooling system. The performance of this system cannot be matched simply by using smaller versions of currently available designs or technologies.

Embodiments of the subject invention relate to an underwater diver heating system that utilizes two-phase heat pump cycle technology. This vapor compression heat pump process can be efficient, such that for a given amount of electrical power supplied to the system at least 2 times that amount of heat, removed from the sea water, is delivered to the diver's body.

In a specific embodiment, the subject invention pertains to a heating system having a total weight of less than about 4.0 pounds, a coefficient of performance of at least 2.4, and a volume of less than about 1200 cc with a heating capacity between about 100 and about 500 watts. In a further embodiment, the subject invention pertains to a heating system having a total weight of less than about 6.0 pounds, a coefficient of performance of at least 1.5, and a volume of less than about 2000 cc with a heating capacity between about 100 and about 500 watts. The subject heating system can provide between 22 and 40 watts of heating per pound and occupy between 2.4 and 12 cc of volume per watt of cooling. In comparison, conventional technology units for heating in this range would between two and three times the amount of battery volume and weight in order to provide the same heating level for a given operation time. Resistive heating devices can only provide a maximum of 1 watt of cooling for every watt of provided electrical energy, thus requiring significantly larger amounts of batteries to provide heat rates similar to the subject invention. Similarly, heating technologies that rely on chemical processes would require a significant amount of large and bulky support equipment

The subject system can be scaled to larger or smaller sizes for different applications. The subject system can incorporate a compressor and heat exchanger design so as to achieve a high coefficient of performance and a light and compact design. Incorporation of a compressor can enhance the overall performance of the vapor compression system, and incorporation of the heat exchanger can reduce the overall weight and size of the subject apparatus. Embodiments of the subject cooling system can utilize a miniaturized, high efficiency motor, along with the integration of compact heat exchangers for refrigerant evaporation and liquid pumps.

Specific embodiments of the subject cooling system can involve the use of one or more of the following: micro-fabrication techniques, an innovative rotary lobed compressor, a miniature high efficiency permanent magnet motor, compact heat exchanger for refrigerant evaporation and condensation, and liquid pumps. In a specific embodiment, the subject system can provide approximately 300 watts of heating or 200 watts of cooling for microclimate and other temperature control environments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an internal view of the interior of an embodiment of the subject invention, illustrating components such as pumps, heat exchangers, compressor, and motors.

FIG. 2 shows an expanded view of a compressor incorporated with the embodiment shown in FIG. 1.

FIG. 3 shows an embodiment of the subject invention, illustrating connections between various parts that allow liquids and/or gases to enter and/or exit the various parts.

FIG. 4 shows an embodiment of an evaporator or condenser in accordance with an embodiment of the subject invention.

FIG. 5 shows the channel design within a condenser or evaporator in accordance with an embodiment of the subject invention.

FIG. 6 shows an Archimedean spiral corresponding to a fluid path within an evaporator in accordance with a specific embodiment of the subject invention.

FIG. 7 shows a schematic of a cooling system in accordance with the subject invention, incorporating a condenser, an expansion valve, an evaporator, and a compressor.

FIG. 8 shows a basic temperature/entropy diagram in accordance with an embodiment of the subject invention.

FIG. 9 shows an embodiment of a heating or cooling system, in the heating configuration, in accordance with the invention incorporating a heat exchanger in an outer shell of the system.

FIG. 10 shows the embodiment of the heating or cooling system of the system of FIG. 9 in the cooling configuration.

DETAILED DISCLOSURE

Embodiments of the subject invention pertain to a method and apparatus for heating or cooling. Embodiments relate to a method and apparatus utilizing a vapor compression cycle to accomplish active heating or cooling. In a specific embodiment, the subject invention relates to a lightweight, compact, reliable, and efficient heating or cooling system for underwater applications. The subject system can provide supplemental heating or cooling to individuals operating in, for example, underwater environments where the loss of control of body temperature or personal comfort can not be mitigated through passive devices such as wetsuits or dry-suits. The subject system can be utilized in other applications that can benefit from this type of heating or cooling system. The performance of this system cannot be matched simply by using smaller versions of currently available designs or technologies.

In a specific embodiment, the subject microclimate system can provide at least about 300 watts of heat while consuming less than about 125 watts of power, and weigh less than about 4.5 pounds (not including the water jacket or the power source) while having less than about a 1200 cubic centimeter volume. In a specific embodiment, the subject system can run for at least about 1.5 hours or more with the use of batteries. In a specific embodiment, a heating power to weight ratio of more than 66 W/lb and/or a volume to heating power ratio of less than 4 cc/W can be achieved utilizing a vapor compression cycle with heating capacities of approximately 300 W.

The same subject microclimate system can provide at least about 200 watts of cooling while consuming less than about 90 watts of power. In a specific embodiment, the subject system can run for at least about 2.0 hours or more with the use of batteries. In a specific embodiment, a cooling power to weight ratio of more than 44 W/lb and/or a volume to heating power ratio of less than 6 cc/W can be achieved utilizing a vapor compression cycle with cooling capacities lower than 200 W.

A heat pump cycle for an embodiment of a microclimate heating and cooling system in accordance with the subject invention can incorporate a vapor compression cycle intended for use with compressible refrigerants. There are four basic features to such a vapor compression cycle, including vapor compression, condensation within a heat exchanger, sub-cooled liquid expansion, and vaporization within an evaporative heat exchanger. The cycle begins with a compressor that compresses refrigerant vapor to a pressure at which the corresponding vapor temperature is above the desired operating fluid temperature of the condenser. This heated fluid can in turn be utilized to provide warmth to the user via, for example, a tube suit or water jacket. The compressed hot refrigerant vapor flows to a condensing heat exchanger, which is typically a gas to vapor or liquid to vapor heat exchanger, where the vapor is hotter than the gas or liquid. Heat is removed from the compressed refrigerant vapor by the entering fluid on the other side of the heat exchanger. This causes the temperature of the compressed, vaporized refrigerant to decrease below the saturation temperature of the refrigerant and the vapor condenses to liquid. The high pressure liquid can then be expanded through an expansion device, such as a throttling valve, capillary tube or pin-hole orifice, which can cause a rapid decrease in refrigerant pressure after the valve. The lower pressure can cause the temperature of the liquid coolant to drop to, for example, the corresponding lower saturation temperature.

In a specific embodiment the expanded, cool liquid refrigerant can then flow through an evaporator that allows the liquid refrigerant to absorb the heat from a fluid that is desired to be cooled. The evaporator can act as another heat exchanger with cool refrigerant on one side and the fluid, either liquid or gas, that is desired to be cooled on the other side of the heat exchanger. The absorption of heat in the evaporator from the entering coolant liquid causes the liquid refrigerant to boil. The vaporized refrigerant then flows back into the compressor to begin the cycle again. The exiting coolant can then be either ejected to the ambient or re-circulated to cool an individual wearing a cooling jacket or to cool surfaces. In the heating mode of operation the evaporator transfers heat from the ambient water to the refrigerant and the condenser transfers heat from the refrigerant to the liquid used to deliver heat. This liquid can deliver heat via, for example, a warming garment. In the cooling mode of operation the condenser transfers heat from the refrigerant to the ambient water and the evaporator transfers heat from the liquid in used to remove heat to the refrigerant.

In a specific embodiment, the subject invention can allow the use of the standard vapor compression cycle in a compact and lightweight design by utilizing specialized components that have been developed specifically for the subject system. FIG. 1 shows a schematic of a heat pump system in accordance with the subject invention, incorporating water pumps 1, an evaporator 2, a compressor 3, a condenser 4, and an expansion device 5. While the subject invention utilizes two similar heat exchangers for the evaporator 2 and the condenser 4, the refrigeration cycle processes of evaporation and condensation can be accomplished with the use of two significantly different custom heat exchangers.

FIG. 7 shows a schematic of a heating system, and FIG. 8 shows a basic vapor compression cycle temperature/entropy diagram. The points 1, 2, 3, and 4 in the heat pump cycle of the heating system of FIG. 7 and the points 1, 2, 3, and 4 in the temperature/entropy diagram of FIG. 8 correspond with each other. Referring to FIG. 8 a compressor intakes cool low pressure vapor refrigerant at point 1. An isentropic compression would discharge hot high pressure refrigerant vapor at point 2 s. However, compressors are not 100% efficient and, therefore, typically exhaust superheated vapor at point 2. The hot, high pressure refrigerant vapor transfers its heat via a heat exchanger, also known as a condenser, to an external fluid. As the hot, high pressure vapor refrigerant cools from point 2 to point 3, it condenses to warm high pressure liquid refrigerant. The warm external fluid side is also further heated by means of conduction, since the heat exchanger is directly in contact with the hot compressor generating additional heat due to the less than 100% efficient compression process. An expansion device located between points 3 and 4 allows the warm high pressure liquid coolant to become a cold low pressure mixture of refrigerant vapor and liquid. The cold low pressure refrigerant then flows to another heat exchanger, typically called an evaporator, to acquire heat from, for example, another external fluid. Alternatively, the evaporator can be in thermal contact with a heat source such that heat is transferred from the heat source to the refrigerant without the use of a second external fluid. This heat transfer causes the low pressure liquid coolant to vaporize, shown in FIG. 8 between points 4 and 1, and becomes cool low pressure refrigerant vapor. Each of the cycle component designs can take size and weight into account.

In an alternative operation mode, where the user desires to circulate cooled liquid in a warm ambient, the re-circulation tubes of a cooling garment or similar device can be attached to the evaporative heat exchange portion of the subject invention. In this mode of operation the compressor, evaporator, condenser, and expansion device may operate in a similar manner while removing heat from the tube suit loop and ejecting heat at an elevated ambient on the condensation side. The liquid side of the condenser can incorporate a liquid pump flowing ambient water through the condensing heat exchanger, which warms the fluid and in turn condenses the refrigerant vapor in point 2 to point 3 of FIG. 8.

In a specific embodiment, one of the two heat exchangers in the system can be located to form at least a portion of an outer shell of the system. A specific embodiment is shown in FIGS. 9 and 10. In the heating system configuration, as shown in FIG. 9, this heat exchanger can function as the evaporator and in the cooling system configuration, as shown in FIG. 10, this heat exchanger can function as the condenser. FIG. 9 shows the heating system configuration with a compressor 3, condenser 4, expansion device 5, evaporator 2, and evaporator outlet port 99. FIG. 10 shows the cooling system configuration with compressor 3, condenser 4, expansion device 5, evaporator 2 and condenser inlet port 98. In a specific embodiment, valving can be provided to allow a single system to both heat and cool by switching the valving depending on the situation.

In a specific embodiment, the subject invention can incorporate compressor 3 shown in FIG. 1. FIG. 2 shows an exploded view of certain portions of compressor 3 shown in FIG. 1. Compressor 3 can utilize a positive displacement means to compress the refrigerant vapor entering the compressor. A positive displacement means can start with a certain volume of refrigerant vapor and reduce the volume by a set amount resulting in compressed refrigerant vapor. The amount of volume change can be a function of the geometry of the positive displacement means. Valves and upstream conditions typically govern the pressure at which the vapor leaves the compressor. The positive displacement means can be, for example, a piston style, a sliding vane, a screw, a scroll, or a rotary lobed type. In a specific embodiment, compressor 3 can incorporate a rotary lobed type positive displacement means. An example of this type of compressor is shown in FIG. 2, and can be referred to as a rotary lobed compressor. The purpose of the compressor is to intake low pressure, low temperature refrigerant vapor and discharge high temperature high pressure vapor to the condenser.

Referring to FIG. 2, the configuration shown can be referred to as a Wankel compressor. The compressor can incorporate a substantially triangular shaped rotor 6 which spins on an eccentric shaft 7. In a specific embodiment, the compressor can use a 3/2 gear ratio for positioning (Ogura, Ichiro, “The Ogura-Wankel Compressor—Application of a Wankel Rotary Concept as Automotive Air Conditioning Compressor,” SAE Technical Paper 820159, SAE 1982). The gears 8 are used to position the rotation of the rotor through its eccentric path. The rotor rotates inside of a peanut shaped epitrochoid chamber 9. Such a rotor positioning results in the compressor exhibiting two complete compressions per revolution.

The shape of an epiterchoid chamber is determined by the following equations:

${x(t)} = {{{\frac{3}{7} \cdot M}\; {A\; \cdot {\cos (t)}}} - {{\frac{1}{14} \cdot M}\; {A \cdot {\cos \left( {3M\; {A \cdot t}} \right)}}}}$ ${y(t)} = {{{\frac{3}{7} \cdot M}\; {A \cdot {\sin (t)}}} - {{\frac{1}{14} \cdot M}\; {A \cdot {\sin \left( {3M\; {A \cdot t}} \right)}}}}$

where MA is the major axis.

In a specific embodiment, a length of 49 mm can be utilized for the major axis of the epitrochoid with a height of 6 mm. The values of the major axis and height can be modified based on the cooling capacity requirements of the vapor compression cycle and the desired angular velocity of the compressor. Once these two constraints are set, the basic designs of the main components of the compressor can be determined as a function of the geometry. The major axis determines the size of the rotor and the shape of the epitrochoid, as well as the gears that are used in the compressor.

Using the equations relating to the shape of the epitrochoid chamber provided above, the rotor size and shape can also be chosen. Finally, the geometric height of the epitrochoid and rotor can be determined by the amount of fluid that is desired to be displaced on each revolution. After having calculated these dimensions, the compressor's speed can be chosen to determine the displacement per unit time or volumetric flow rate. In a specific embodiment, incorporating an epitrochoidal chamber with a major axis of 49 mm and a height of 6 mm, a speed of 2000 rpm is chosen to provide a mass flow rate of approximately 1.5 g/s of vapor refrigerant 134 a at an inlet pressure of 50 psi.

The flow through the compressor can be controlled by inlet port 10 (shown in FIG. 2) and valved exhaust ports 11 (shown in FIG. 2). Although a round shaped port is shown here, other shapes such as oval, triangular, and square can also be used. This design can allow the cool refrigerant vapor into the compressor. Rotor 6 can then travel over the top of the intake port so as to close the intake port as rotor 6 begins to compress the refrigerant vapor. This feature can eliminate the need for an intake check valve, typically used by positive displacement compressors. Exhaust valve 12 and valve stop 13 can be placed on the top face of the compressor and positioned on top of the exhaust port 13 to allow for the maximum compression to occur. The exhaust valve is a check valve that can prevent hot high pressure refrigerant vapor from flowing backwards into the compressor. In a specific embodiment, cantilevered flapper valves can be used to reduce the amount of space required for the outlet port 11.

Shaft seals and bearings can be used along the shaft to assist in sealing and to absorb the loads caused by the rotating parts. External sealing can be achieved by the shaft seals and gaskets or by encapsulating the entire compressor and driving motor unit in a hermetic casing, while internal sealing of the compression chambers can be accomplished using, for example, a sealing gasket 14 or o-ring.

To increase the efficiency and life of the compressor, referring to FIG. 2, spring loaded tip seals 15 can be installed on the rotor. The tip seals 15, as shown in FIG. 2, can be designed to minimize leakage between the chambers during the rotary motion of the rotor. In a specific embodiment, the seals or entire rotor can be made of a low friction material to minimize wear and friction losses. In a further specific embodiment, an engineered plastic material such as PEEK, TEFLON, NYLON, or DELRIN can be used. Other materials with similar characteristics can also be used. The tip seals and face seals are spring loaded to insure that the plastic seals stay in contact with the metal surfaces of the compressor housing. In a specific embodiment, the springs used are 2.4 mm in diameter, 6.2 mm long, have a spring stiffness constant of 2.2 lbs per inch, and a pitch of 35 coils per inch. Preferably, at least one spring is used on each of the tip seals. Multiple springs can be used on the face seal in order to provide an even spring loading force or additional spring force. In further embodiments, the spring force can be produced by other means such as wave springs, elastic rubbers, or gas filled balls. Preferably, the tip and face seals are fabricated so that a slip fit into the rotor can be maintained. In a specific embodiment, a slip fit dimensional tolerance of less than or equal to 8 microns is used.

Additional methods of sealing may be considered for the compressor as well. Rather than face sealing with gaskets and spring loaded plastics, sufficient sealing can be created by machining the parts with very high precision. In a specific embodiment, the gaps between the rotor and the upper or lower walls are machined to fit to within a range of between 0.0001 and 0.002 inches so that the fluid being pressurized has significant difficulty in leaking past the two surfaces.

The subject compressor can incorporate low friction, low corrosion materials. In addition, wear parts other than the seals can be coated with low friction, high hardness coating, such as diamond like carbon, TiN, and MoSi₂. In a specific embodiment, the subject compressor can operate without coolant oil. Compressor oil can reduce the heat transfer performance of the condenser and evaporators, requiring a larger heat exchanger to properly transfer heat. Accordingly, the use of a specific embodiment of the subject compressor that can operate without oil can allow the use of a smaller heat exchanger.

The motor 16 as shown in FIG. 3, can be used to power the drive shaft 17. In a specific embodiment, the motor 16 can be a permanent magnetic synchronous motor. Other mechanical devices capable of producing shaft power can also be used to power the subject compressor, including, for example, combustion engines, wind, or paddlewheels. In a specific embodiment, the motor can be designed for long service life and can operate at much higher efficiencies than standard motors. The motor design can be a compact unit specially suited for this type of application. The motor can deliver a high power density and operate at variable speeds through a motor controller. The incorporation of a motor controller can allow the motor to change the amount of compression, depending on the cooling load. Standard vapor compression cycles typically turn the compressor on and off in order to adjust to the net cooling requirements of the cooling load. The turning of the compressor on and off can reduce the efficiency of the cooling system, as the start up interval of a motor can be extremely inefficient. Accordingly, the use of a control feature, in a specific embodiment of the subject invention, can allow the variation of the speed of the motor, rather than intermittent operation of the motor, to adjust the cooling system to the net heating requirement of the heating load so as to significantly improve the energy efficiency of the cycle. In a specific embodiment, the motor can provide 90 Watts of shaft power, provide 60 oz-in torque, weigh approximately 16 ounces, have a diameter of 1.9 inches, and have a maximum efficiency of 78%.

The subject cooling system can be powered by, for example, by batteries, AC power, or DC power. An embodiment powered by batteries can connect to external battery packs or can utilize a central power unit.

The compressed vapor refrigerant exiting outlets 18 of the compressor can flow into a condenser inlet port 19, shown in FIG. 2 and FIG. 3, via connection passageway 20, shown in FIG. 3. The condenser can be, for example, a general purpose heat exchanger. On a first side of the heat exchanger the compressed hot refrigerant gas can flow and on a second side of the heat exchanger an external fluid can flow. Typically, water can be used on the second side of the heat exchanger, thus providing heated water to the user if it is connected to the condensation side, or cooled water to the user if it is connected to the evaporation side. The heat is transferred between the two fluids via dividing wall 21 (shown in FIG. 3, FIG. 4 and FIG. 5) such that an external fluid flowing on the outer surface, or heat transfer surface 22, of dividing wall 21 will remove heat from the dividing wall which has absorbed heat from the refrigerant flowing through the condenser. The design of the subject condenser can involve optimizing the heat transfer between the two fluids flowing on either side of dividing wall 21.

A specific embodiment of a condenser 4 in accordance with the subject invention is shown in FIG. 1, FIG. 3, and FIG. 4. The compressed vapor refrigerant enters the refrigerant condensation path 22 after passing through the exiting outlets 18. The refrigerant can exit the condenser via port 23 and enter an expansion device. Sub-cooled high pressure liquid refrigerant can flow from the condenser 4 via connection tube 24 (shown in FIG. 3) or expansion device into evaporator 2 (shown in FIG. 2 and FIG. 4). An embodiment of evaporator 2 can have a similar design to condenser 4, where two channels of two different fluids are in indirect contact by dividing wall 21 and exchange heat via dividing wall 21. These fluids can travel in their respective channels in co-planar, multi-planar, counter rotating, or co-rotating fashion, while exchanging heat with the opposite fluid via the heat transfer surface 22 and the dividing wall 21. The cooled, compressed liquid refrigerant can travel through connector tube 24 and enter evaporator 2 via, for example, a throttling device. The device can be a simple port design that causes a long restriction to the flow via the port diameter, a capillary tube type, or a commercially available expansion valve that is preset, manually adjustable, electrically controlled, thermally controlled, or controlled by system pressure.

The liquid that is to be heated can enter the condenser via liquid connection tube 24 and travel to liquid port 25. A pump 1 can pump the heated liquid through the heating path 26. In a specific embodiment, pump 1 is built into the condenser. Alternatively, a pump external to the condenser or external to the entire heat pump system can be utilized. The heated liquid can exit the condenser via fluid exit port 27 and flow out of connection tube 28. The heated liquid type can vary depending on the application and can be, for example, a liquid, gas, or two-phase mixture. The geometry of the heat exchanging condenser can vary depending on the type of fluid and required performance. In a specific embodiment, the liquid is water. Although the embodiment shown in FIGS. 1, 3, 4, and 5 incorporates counter rotating fluids that are co-planar, the subject invention can also incorporate co-rotating fluids in the condenser or fluids that are not co-planar.

The subject condenser can exchange heat between a liquid and the refrigerant. While the refrigerant passes through the condensing heat exchanger, it can experience a phase change from vapor to liquid as it loses heat to the heated liquid on the opposing side. With respect to this atypical heat exchanger, non-traditional methods can be utilized for predicting the performance of and designing of the heat exchanger. The liquid side can adhere to well established heat transfer correlations, which suggest that the total heat transfer between two substances at different temperatures is equal to a heat transfer coefficient constant times the total area that it is acting on and the temperature gradient.

Heat transfer characterization and prediction on the refrigerant side, however, is more complicated due to the phase change process that occurs while the refrigerant is passing through the heat exchanger. Approximate correlations, which include experimental correction factors, have been recently determined and are discussed in detail in Carey, Van P., Liquid-Vapor Phase Change Phenomena, Taylor and Francis, New York (1992), which is hereby incorporated by reference. A specific embodiment of the subject invention can utilize a heat exchanger geometry that is based on correlation approximations from Carey (1992) that maximize the amount of heat transfer on the refrigerant side from the heated liquid on the other side.

Similar to the heated liquid side, however, the two phase heat transfer phenomenon is highly dependent upon the amount of area available for heat transfer to take place. In a specific embodiment, the design of the subject condensing heat exchanger can, in general, maximize heat transfer area, while minimizing overall weight and dimensions and minimizing the liquid pressure drop through the heat exchanger. Preferably, the two fluids pass as close to each other as possible in order to minimize conduction heat transfer resistance through the separating medium. In a specific embodiment, a parallel channel construction configuration can be utilized. In a further specific embodiment, the parallel channel configuration can have a separation wall of 0.5 mm and can follow the path of an Archemedian spiral. An archemidian spiral is defined in a parametric coordinate system as:

x(t)=A·t·cos(B·t)

y(t)=A·t·sin(B·t)

where the constants A and B govern the number of spiral revolutions and the overall diameter of the geometry. One example yields a spiral path as is seen in FIG. 6. The path shown in FIG. 6 can be used for one fluid, while rotating the path by 180 degrees can provide a path to be used by the second fluid. In other embodiments, other interdigitated spiral paths can also be utilized.

In a specific embodiment, the path for both fluids can begin on the outer edge of the cylinder and terminate in the center, where both fluids can exit perpendicular to the plane that they are flowing parallel on. Such a design can eliminate abrupt fluid turning points, thus minimizing pressure drop. Thin separation walls can be used to provide a sufficient length of, for example, approximately 26 inches within the limited area of the condenser having a diameter of 2.2 inches. The channel depth can be chosen, using two-phase heat transfer correlations as a guide, to maximize the heat transfer area available for both fluids and meet the heat exchange rate requirements of the condenser.

Condensed high pressure liquid refrigerant can flow from the condenser 4 via exit port 23 (shown in FIG. 3 and FIG. 5) into evaporator 2 (shown in FIG. 1 and FIG. 3). This heat exchange device is similar in design to the condenser component (4), but is applied as an evaporator at this point of the refrigeration cycle. The cooled, compressed liquid refrigerant can travel through connector tube 5 and enter evaporator 2 via, for example, a throttle device. The device can be a simple port design that causes a large restriction to the flow via the port diameter, a capillary tube type, or an expansion valve that is preset, manually adjustable, electrically controlled, thermally controlled, or controlled by system pressure. The coolant that is to be cooled can enter the evaporator via coolant connection tube 36 and travel to coolant port 37. A pump 1 can pump the coolant through the cooling path 29. The expanding liquid cools and enters refrigerant evaporation path 29. The refrigerant can exit the evaporator via port 30 and enter a connection tube 31 that terminates at the compressor motor housing chamber 32. From one extreme location of the motor chamber (point 32) the fluid can traverse the motor components (16 and 33) and enter the compressor via inlet ports (34) and populate in inlet manifold distribution area (35).

A specific embodiment of the subject compact vapor compression cooling system, shown in FIG. 1 and FIG. 3, can employ a compact assembly that reduces empty space. A cylindrical shape enhances the surface area of several of the components of the vapor compression cycle such as the heat exchangers so as to reduce the volume of the system. In a specific embodiment, the cylindrical shape can allow for ease of assembling of the components, along with enhanced surface area to volume ratios of the heat exchanger components. Each of the components can be designed into cylindrical shapes, with similar diameters. The components can then be stacked together and inserted inside a container (38). This design can provide an efficient, low mass, low volume vapor compression cycle.

All patents, patent applications, provisional applications, and publications referred to or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.

It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application. 

1. An apparatus for heating, comprising: an evaporator; a compressor, wherein the compressor receives refrigerant vapor exiting from the evaporator, wherein the compressor compresses the refrigerant vapor received from the evaporator; a condenser, wherein compressed refrigerant exits the compressor and flows into the condenser, wherein the condenser acts as a heat exchanger so that heat is removed from the compressed refrigerant by a first external fluid; an expansion device, wherein the expansion device receives refrigerant from the condenser, wherein the refrigerant received from the condenser is expanded through the expansion device; wherein the refrigerant exiting the expansion device flows through the evaporator, wherein the refrigerant absorbs heat from a second external fluid as the refrigerant passes through the evaporator; and a housing, wherein the condenser and the evaporator are within the housing.
 2. The apparatus according to claim 1, wherein the condenser comprises a pair of channels, wherein the refrigerant flows through one of the channels of the pair of channels and the first external fluid flows through the other channel of the pair of channels such that the refrigerant and the first external fluid flowing in the pair of channels are in thermal contact with each other.
 3. The apparatus according to claim 1, wherein the evaporator comprises a second pair of channels, wherein the refrigerant flows through one of the channels of the second pair of channels and the second external fluid flows through the other channel of the second pair of channels such that the refrigerant and the second external fluid flowing in the second pair of channels are in thermal contact with each other.
 4. The apparatus according to claim 2, wherein the evaporator comprises a second pair of channels, wherein the refrigerant flows through one of the channels of the second pair of channels and the second external fluid flows through the other channel of the second pair of channels such that the refrigerant and the second external fluid flowing in the second pair of channels are in thermal contact with each other.
 5. The apparatus according to claim 1, wherein the compressor and the expansion device are within the housing.
 6. The apparatus according to claim 1, wherein the housing is substantially tubular.
 7. The apparatus according to claim 6, wherein the housing is substantially cylindrical, wherein the condenser is substantially cylindrical in shape, wherein the pair of channels spiral from a center of the condenser to an outer portion of the condenser, wherein the evaporator is substantially cylindrical in shape, where the second pair of channels spiral from a center of the evaporator to an outer portion of the evaporator.
 8. The apparatus according to claim 4, wherein the pair of channels are parallel, wherein the second pair of channels are parallel.
 9. The apparatus according to claim 1, further comprising: a power source, wherein the power source powers the compressor wherein the power source is proximate the housing.
 10. The apparatus according to claim 1, wherein the second external fluid is air.
 11. The apparatus according to claim 9, wherein the second external fluid is water.
 12. The apparatus according to claim 1, wherein the first external fluid is water.
 13. The apparatus according to claim 1, wherein the temperature of the compressed refrigerant vapor flowing through the condenser decreases below the saturation temperature of the refrigerant and the refrigerant vapor condenses to liquid refrigerant, wherein the liquid refrigerant exits the condenser and is expanded through the expansion device, wherein the pressure and temperature of the liquid refrigerant are reduced upon exiting the expansion device, wherein the liquid refrigerant exiting the expansion device flows through the evaporator, wherein the liquid refrigerant and the second external fluid are in thermal contact, wherein the liquid refrigerant absorbs heat from the second external fluid as the liquid refrigerant passes through the evaporator such that the liquid refrigerant boils to produce vapor, wherein the vapor exits the evaporator, and wherein the compressor receives the refrigerant vapor exiting from the evaporator, wherein the compressor compresses the refrigerant vapor to a pressure at which the vapor temperature is above the ambient temperature of the condenser, wherein the compressed refrigerant vapor exits the compressor and flows into the condenser.
 14. The apparatus according to claim 1, further comprising a pump, wherein the pump causes the first external fluid to flow through the condenser.
 15. The apparatus according to claim 7, wherein the compressor is substantially cylindrical in shape.
 16. The apparatus according to claim 15, further comprising: a motor, wherein the motor is substantially cylindrical in shape, and wherein the motor drives the compressor wherein the motor is within the housing.
 17. The apparatus according to claim 1, wherein the housing seals the condenser, the evaporator, the compressor, and the expansion device from a surrounding environment outside the housing, wherein the first external fluid entering the housing through a first input port and exits the housing through a first output port, wherein the second external fluid enters the housing through a second input port and exits the housing through a second output port.
 18. The apparatus according to claim 1, wherein heat from the first external fluid is transferred to a user.
 19. The apparatus according to claim 1, wherein the first external fluid is circulated from an output of the condenser to the user, from the user to an input of the condenser, and from the input of the condenser through the condenser to the output of the condenser.
 20. An apparatus for heating, comprising: an evaporator; a compressor, wherein the compressor receives refrigerant vapor exiting from the evaporator, wherein the compressor compresses the refrigerant vapor received from the evaporator; a condenser, wherein compressed refrigerant exits the compressor and flows into the condenser, wherein the condenser acts as a heat exchanger so that heat is removed from the compressed refrigerant by a first external fluid; and an expansion device, wherein the expansion device receives refrigerant from the condenser, wherein the refrigerant received from the condenser is expanded through the expansion device, wherein the refrigerant exiting the expansion device flows through the evaporator, wherein the refrigerant absorbs heat from a second external fluid as the refrigerant passes through the evaporator; wherein the evaporator comprises a heat transfer surface in contact with a surrounding environment, wherein the surrounding environment is the second external fluid.
 21. The apparatus according to claim 20, wherein the second external fluid is a liquid.
 22. The apparatus according to claim 21, wherein the first external fluid is water.
 23. The apparatus according to claim 20, wherein the second external fluid is water.
 24. The apparatus according to claim 20, wherein the second external fluid is air.
 25. The apparatus according to claim 24, further comprising a fan, wherein the fan moves air across the heat transfer surface.
 26. The apparatus according to claim 20, wherein the evaporator comprises a dividing wall having an interior surface and an exterior surface, wherein the interior surface is in thermal contact with the refrigerant exiting the expansion device and the exterior surface is the heat transfer surface.
 27. The apparatus according to claim 20, wherein the evaporator comprises a second surface, wherein the heat transfer surface is on the exterior side of the evaporator and the second surface is on the interior side of the evaporator, and wherein a volume is formed by the second surface of the evaporator.
 28. The apparatus according to claim 27, wherein the evaporator has a substantially tubular shape having a first end and a second end.
 29. The apparatus according to claim 27, wherein the second surface is substantially parallel to the heat transfer surface.
 30. The apparatus according to claim 28, wherein the compressor is positioned within the volume created by the second surface of the evaporator.
 31. The apparatus according to claim 30, wherein the condenser is positioned within the volume created by the second surface of the evaporator.
 32. The apparatus according to claim 31, wherein the expansion device is positioned within the volume created by the second surface of the evaporator.
 33. The apparatus according to claim 20, wherein the surrounding environment is water, wherein the surrounding water flows across the heat transfer surface of the evaporator.
 34. The apparatus according to claim 20, further comprising switching valves, wherein the switching valves allow the apparatus to remove heat from the first external fluid by driving the evaporator as a second condenser and driving the condenser as a second evaporator.
 35. The apparatus according to claim 20, wherein the first external fluid flows through the condenser such that the refrigerant and the first external fluid are in thermal contact, wherein the first external fluid absorbs heat from the refrigerant as the refrigerant flows through the condenser.
 36. The apparatus according to claim 35, wherein the temperature of the compressed refrigerant vapor flowing through the condenser decreases below the saturation temperature of the refrigerant and the refrigerant vapor condenses to liquid refrigerant, wherein the liquid refrigerant exits the condenser and is expanded through the expansion device, wherein the pressure and temperature of the liquid refrigerant are reduced upon exiting the expansion device, wherein the liquid refrigerant exiting the expansion device flows through the evaporator, wherein the liquid refrigerant and the second external fluid are in thermal contact, wherein the liquid refrigerant absorbs heat from the second external fluid as the liquid refrigerant passes through the evaporator such that the liquid refrigerant boils to produce vapor, wherein the vapor exits the evaporator, and wherein the compressor receives the refrigerant vapor exiting from the evaporator, wherein the compressor compresses the refrigerant vapor to a pressure at which the vapor temperature is above the ambient temperature of the condenser, wherein the compressed refrigerant vapor exits the compressor and flows into the condenser.
 37. The apparatus according to claim 20, wherein the refrigerant that absorbs heat from the surrounding environment in thermal contact with the heat transfer surface flows through the evaporator such that the flow of the refrigerant is substantially parallel to the heat transfer surface.
 38. The apparatus according to claim 28, wherein the evaporator has a cross-sectional shape selected from a group consisting of: rectangular, polygonal, square, hexagonal, peanut, and oval.
 39. The apparatus according to claim 28, wherein the evaporator has a substantially circular cross-sectional shape.
 40. The apparatus according to claim 20, further comprising a pump, wherein the pump causes the first external fluid to flow through the condenser.
 41. The apparatus according to claim 39, wherein the compressor is substantially cylindrical in shape.
 42. The apparatus according to claim 41, further comprising: a motor, wherein the motor is substantially cylindrical in shape, and wherein the motor drives the compressor.
 43. The apparatus according to claim 42, wherein the motor is positioned substantially within the volume formed by the second surface of the evaporator.
 44. The apparatus according to claim 27, wherein the condenser comprises a pair of channels wherein the refrigerant flows through one of the channels of the pair of channels and the first external fluid flows through the other channel of the pair of channels such that the refrigerant and the first external fluid flowing in the pair of channels are in thermal contact with each other.
 45. The apparatus according to claim 44, wherein the condenser is substantially cylindrical in shape.
 46. The apparatus according to claim 44, wherein the pair of channels spiral from the center of the condenser to the outer portion of the condenser.
 47. The apparatus according to claim 44, where the pair of channels are parallel.
 48. The apparatus according to claim 47, wherein each channel of the pair of parallel channels substantially follows the path of a corresponding archemidian spiral.
 49. The apparatus according to claim 20, wherein heat from the first external fluid is transferred to a user positioned in the surrounding environment.
 50. The apparatus according to claim 49, wherein the first external fluid is circulated from an output of the condenser to the user, from the user to an input of the condenser, and from the input of the condenser through the condenser to the output of the condenser.
 51. A method for heating, comprising: attaching an apparatus to a user positioned in a second external fluid, wherein the apparatus comprises: an evaporator; a compressor, wherein the compressor receives refrigerant vapor exiting from the evaporator, wherein the compressor compresses the refrigerant vapor received from the evaporator; a condenser, wherein compressed refrigerant exits the compressor and flows into the condenser, wherein the condenser acts as a heat exchanger so that heat is removed from the compressed refrigerant by a first external fluid; and an expansion device, wherein the expansion device receives refrigerant from the condenser, wherein the refrigerant received from the condenser is expanded through the expansion device; wherein the refrigerant exiting the expansion device flows through the evaporator, wherein the refrigerant absorbs heat from a second external fluid as the refrigerant passes through the evaporator; wherein the evaporator comprises a heat transfer surface in contact with a surrounding environment, wherein the surrounding environment is the second external fluid; and bringing the first external fluid in thermal contact with the user such that heat from the first external fluid is transferred to the user.
 52. The method according to claim 51, wherein the apparatus further comprises: a power source, wherein the power source powers the compressor.
 53. The method according to claim 51, further comprising: attaching a power source to the user, wherein the power source powers the compressor.
 54. The method according to claim 51, wherein the first external fluid is circulated from an output of the condenser to the user, from the user to an input of the condenser, and from the input of the condenser through the condenser to the output of the condenser.
 55. A method for heating, comprising: attaching an apparatus to a user positioned in a second external fluid, wherein the apparatus comprises: an evaporator; a compressor, wherein the compressor receives refrigerant vapor exiting from the evaporator, wherein the compressor compresses the refrigerant vapor received from the evaporator; a condenser, wherein compressed refrigerant exits the compressor and flows into the condenser, wherein the condenser acts as a heat exchanger so that heat is removed from the compressed refrigerant by a first external fluid; an expansion device, wherein the expansion device receives refrigerant from the condenser, wherein the refrigerant received from the condenser is expanded through the expansion device, wherein the refrigerant exiting the expansion device flows through the evaporator, wherein the refrigerant absorbs heat from a second external fluid as the refrigerant passes through the evaporator; and bringing the first external fluid in thermal contact with the user such that heat from the first external fluid is transferred to the user.
 56. The method according to claim 55, wherein the condenser comprises a pair of channels, wherein the refrigerant flows through one of the channels of the pair of channels and the first external fluid flows through the other channel of the pair of channels such that the refrigerant and the first external fluid flowing in the pair of channels are in thermal contact with each other.
 57. The method according to claim 55, wherein the evaporator comprises a second pair of channels, wherein the refrigerant flows through one of the channels of the second pair of channels and the second external fluid flows through the other channel of the second pair of channels such that the refrigerant and the second external fluid flowing in the second pair of channels are in thermal contact with each other.
 58. The method according to claim 55, wherein the apparatus further comprises: a housing, wherein the condenser and the evaporator are within the housing.
 59. The method according to claim 58, wherein the compressor and the expansion device are within the housing.
 60. The method according to claim 55, wherein the first external fluid is circulated from an output of the condenser to the user, from the user to an input of the condenser, and from the input of the condenser through the condenser to the output of the condenser.
 61. The method according to claim 55, wherein the apparatus is attached to a back of the user.
 62. The method according to claim 55, wherein the apparatus further comprises: a power source, wherein the power source powers the compressor.
 63. The method according to claim 55, further comprising: attaching a power source to the user, wherein the power source powers the compressor. 